Conventionally, a technology that constitutes a battery unit by providing a battery pack module that has a plurality of single cells together with a control circuit board etc. unitarily is known (refer to Japanese Patent Application Laid-Open Publication No. 2011-216401, for example).
Moreover, installing such a battery unit in vehicles is proposed.
In a composition that the battery unit is installed in the vehicle, submergence of the battery unit is detected by a submergence sensor disposed in the battery unit, when the vehicle is flooded with water.
In this case, control sections such as a CPU mounted on a control circuit board perform a process that suspends a charge-and-discharge function of the battery pack module and the like according to a detected result of the submergence sensor.
However, if submergence of the battery unit is not appropriately detected when the vehicle is flooded with water or it goes into a puddle, various inconveniences will occur.
For example, if water is detected by the submergence sensor even though only a small amount of water enters the battery unit, and in fact that water level is not raised, an incorrect detection that the battery unit is in a submerged condition is produced, and functions of the battery unit such as the charge-and-discharge function of the battery pack module may be suspended unnecessarily.
On the other hand, if water is not easily detected in spite of the water level actually being raised, that is, in a composition that the water is detection by the submergence sensor only just before a submergence of a control section in the battery unit, it is possible that a control facility of the control section is suspended before it can suspend the battery charge and discharge, etc., and, in this case, it becomes impossible to performing proper countermeasure against flooding.